Abstract

We report a thirteen-year-old tennis player with knee hemarthrosis caused by low factor
XIII activity. She visited our hospital because of medial peripatellar pain for two
years. Although there was no abnormal sign in X-ray or MRI, diagnostic arthroscopy
was performed. It revealed some cartilage debris, medial plica and complete septum
of suprapatellar plica. Removing the debris by washing out and resecting the medial
plica, she could return to play tennis without perioperative symptom. Two months after
the first operation, her knee got swelling without any apparent cause. Since 20 ml
blood was aspirated twice and MRI revealed suprapatellar mass, we performed arthroscopy
again. Suprapatellar mass was old blood clot covered with complete suprapatellar plica.
Resection of suprapatellar plica and washing out blood clot were performed, and severe
postoperative hemarthrosis was progressively occurred. As factor XIII level was 54%
preoperatively, we diagnosed that this condition was caused by low activity level
of the factor and administered factor XIII concentrates. The level got improved to
129% and then hemarthrosis gradually relieved. She had no signs of recurrence. We
should keep in mind of low factor XIII activity case in case of unexplained postoperative
hemarthrosis after arthroscopy because consumption of the factor might promote this
condition.